Boomerang Nebula Temperature

[vintersorg]

From wiki: "With a temperature of -272 °C, it is only 1 degree kelvin warmer than absolute zero (the lowest limit for all temperatures)."<br /><br />How can we measure the temperature of a nebula 5000LY away? Also, how can it reach such a cold state? I hope this is not too much to ask <img src="/images/icons/smile.gif" /><br /><br />Edit: The gas is moving outwards at a speed of about 164 km/s and expanding rapidly as it moves out into space. This expansion is the cause of the nebula's very low temperature<br /><br />This kind of answers my second question.<br /><br />Thanks.

 

[billslugg]

Temperatures can be measured from great distances by using a sensitive radio receiver and a very large and very accurate dish antenna. Using the 15 meter Swedish ESO submillimeter telescope in Chile, Sahai and Nayman were able to measure the vibration frequency of carbon monoxide molecules. The sensitive receiver and the large diameter of the telescope allows measurement of a very weak signal, and the large diameter and the accuracy of the dish allows a very narrow beam width, so they know that the signal is, in fact, coming from the Boomerang nebula.<br /><br />The conditions that produce a temperature lower than the background mimic a refrigerator. In this case it appears to be a rapidly spinning red giant that ran out of fuel, shed its outer layers, and collapsed to a white dwarf. By spinning rapidly it is presumed to have a strong magnetic field. The shed outer layers of the red giant are composed of ionized gas. Such a plasma is comprised of charged particles. They cannot cross magnetic field lines, but can only travel along them. With a strong bipolar magnetic field, the plasma can only exit the star along the north and south pole. Given that so much gas is exiting in such a small area, it must be compressed. Since the star has run out of fuel, there is relatively little heat input to the gas. The length of each jet is about 1 light year. As it leaves the vicinity of the white dwarf, it loses all of its heat to the dark sky. It is still somewhat compressed, thus as it continues to expand and cool, it will drop below the 3 degree kelvin background. <div class="Discussion_UserSignature"> <p> </p><p> </p> </div>

 

[richalex]

Did the standards body change the convention? I was told that kelvin doesn't use degree. So, the gas is 1 kelvin warmer than absolute zero (which is the same as it being 1 degree Celsius warmer than absolute zero).

 

[vintersorg]

Sorry, I'm used to using Celsius. I should've used Kelvin. It is indeed one degree away from absolute zero, that's what amazed me the most.<br /><br />Anyway, thank you all for your answers and the model. That was really helpful.

 

[nexium]

Yes, thankyou. Neil